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Discussion Starter · #1 ·
My buddy's 06 F4i isn't working properly. When the key is turned on the fuel pump does not prime. We bypassed the tip-over switch, so that is not the issue. All of the fuses are good and tried switching around the two relays on the right side of the subframe around and that didn't work either. I put a test light to the fuel pump to see if it is getting power, it is but just barely enough to light up my test light. Is this because the ecu only puts out so much power? We tried jumping the fuel pump but were also unsuccessful. So, I know the fuel pump is getting some power. Any other ideas?
 

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Function IS Form
19 Z900, 88 Kat11
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You gave the fuel pump power directly, from the battery, is that what mean by 'jumped it'?

If so then you need to check the fuel pump ground, which you can do with most test lights.

If the ground is fine, then the fuel pump has failed.
 

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Discussion Starter · #3 ·
You gave the fuel pump power directly, from the battery, is that what mean by 'jumped it'?

If so then you need to check the fuel pump ground, which you can do with most test lights.

If the ground is fine, then the fuel pump has failed.
Thanks for the quick response. I'm tired and had a long day...Pretend I am a complete moron and explain how exactly I should test the ground properly.

In the meantime I'll be in the other room working on another bike. It never ends.....
 

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Function IS Form
19 Z900, 88 Kat11
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Put a pin in the test light's ground clamp and stick it into where the ground wire goes into the plug on the fuel pump. Then put the test light's spike into a circuit you know is good (easy one is the headlight usually). If the test light lights up, it means it's using the fuel pump ground as a ground successfully.

If the ground is good, the fuel pump failed.
If the ground is bad, then repair the ground :)
The ground being bad may be because of a broken switch (if there are any ground-switches for the fuel pump on that bike), a broken wire, a loose ground bolt, a rusted ground (not common on bikes, but plausible)
 

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Function IS Form
19 Z900, 88 Kat11
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You can't poke the ground wire with the test light attached to another ground
you gotta poke the ground wire with one end of the test light, and poke a hot wire with the other end (a powered up hot wire)

just to clarify
 

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Discussion Starter · #8 ·
You can't poke the ground wire with the test light attached to another ground
you gotta poke the ground wire with one end of the test light, and poke a hot wire with the other end (a powered up hot wire)

just to clarify
A powered up hot wire like the positive lead from the battery, correct?
 

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Function IS Form
19 Z900, 88 Kat11
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I usually use the other side of the circuit (IE, the power wire to the fuel pump) but you said the light was dim. I wonder if it's bright on that side or still dim... so I'd suggest a headlight or a taillight or a turn signal or a gauge power wire
or the positive battery terminal
 

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Discussion Starter · #10 ·
I don't understand why it would be dim... doesn't make any sense to me. Is that because the ecu puts out less than 12v?
 

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Function IS Form
19 Z900, 88 Kat11
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The fuel pump is relayed. The computer puts 5v to the relay, which lets 12v go to the fuel pump. The pump runs on 12v, in other words.

It would be dim because of high resistance in the power or ground wires, or a poor ground for the test light (IE, your clamp wasn't clamped on a good ground when poking the power wire)

You'd need a continuity tester or a multimeter to test the resistance in either wire.

I don't think it has high resistance in the power wire, because you said you jumped the pump directly to a power source, if I recall correctly, which means that the reason the pump isn't running isn't because of a lack of power.
 

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Discussion Starter · #12 ·
The fuel pump is relayed. The computer puts 5v to the relay, which lets 12v go to the fuel pump. The pump runs on 12v, in other words.

It would be dim because of high resistance in the power or ground wires, or a poor ground for the test light (IE, your clamp wasn't clamped on a good ground when poking the power wire)

You'd need a continuity tester or a multimeter to test the resistance in either wire.

I don't think it has high resistance in the power wire, because you said you jumped the pump directly to a power source, if I recall correctly, which means that the reason the pump isn't running isn't because of a lack of power.

There are 3 wires coming from the pump, a ground obviously and 2 others. I ran 12v each of the wires with a good ground and nothing happened. Wouldn't it turn over just like an electric motor?
 

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yeah. One of those wires is for the fuel level sensor. The sensor and the pump share a ground.
 

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Discussion Starter · #18 ·
Okay we checked the fuel pump again and it is working now. Got ahold of the honda manual and checked everything we could. All the relays are working. The bike is not getting spark, we figured this out by running power to the fuel pump and a toggle switch. We checked for codes and it is not showing any, so we have deduced that the ECM is faulty. The books says to test the ECM take it to a Honda dealer. What do you guys think? My buddy is getting depressed...don't think he'll make ride of the century this year.
 

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19 Z900, 88 Kat11
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Did you check the coils, CDI, cam sensor? You can't rely entirely on the computer for diagnostics.
 

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so the computer wont throw a code for uncommanded fuel pump output ? and since your on a toggle it wont throw a secondary fuel output circuit high code ?
 
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